Electronic devices such as mobile phones, smart phones, and other handheld or portable electronic devices such as personal digital assistants (PDAs), audio players, headsets, etc. have become popular and ubiquitous. As more and more features have been added to such devices, there has been an increasing desire to equip them with input/output mechanisms that accommodate numerous user commands and/or react to numerous user behaviors. For example, many mobile devices are now equipped not only with various buttons and/or keypads, but also with touch-detecting surfaces such as touch screens or touch pads by which a user, simply by touching the surface of the mobile device and/or moving the user's finger along the surface of the mobile device, is able to communicate to the mobile device a variety of instructions.
A so-called multi-touch touch-detecting surface allows for the detection of multiple touches that occur simultaneously, while a single-touch touch-detecting surface only allows for the detection of a single touch at a time. Multi-touch surfaces are advantageous in that various gesture combinations performed using two or more simultaneous touches (such as using two fingers) are detectable, so that a richer and more varied set of device functions (such as scaling and translation) can be controlled in a straightforward manner. For example, two fingers moving apart on a multi-touch touch-detecting surface can be used to zoom out on an associated map or document or photograph, while two fingers moving together can be used to zoom in. Also, two fingers moving together across a multi-touch touch-detecting surface can be used to translate an item at twice the speed compared to moving just one finger across the touch-detecting surface. However, multi-touch touch-detecting surfaces are in general more expensive and complex than single-touch touch-detecting surfaces, so that single-touch surfaces are advantageous from a cost and simplicity standpoint. Further, in certain circumstances, it can be difficult for a user to interact with an electronic device using simultaneous touches, such as when a user has only one finger (e.g., a thumb) available for touch interaction or otherwise has limited finger mobility due to, for example, injury or arthritis.